So I had a thought today, and I wanted to figure out if it's correct or not about centripetal force. I've always heard it described as the inward force something experiences as it goes around a curve. But could it better be described as the force necessary for an object to maintain circular motion at a given radius and velocity? Because F_c always has to be accounted for with other forces (tension, gravity, friction). So F_c is not a force itself like friction or gravity is. It's just what we call whatever real force/forces is/are causing the inward acceleration that causes circular motion. This came about because someone was asking if centripetal force is inward, Newton's Third Law should have an outward force as well. I expained that the outward force is on whatever is causing the inward force (on the other end of the string, the object being orbitted, the other frictious surface, etc...). This led to the fact that F_c is always caused by something else, which led to the fact that F_c = mv^2/r is just a way for us to know what force is necessary to maintain the circular motion for a given r and v, but it doesn't actually account for the force.